Plate type heat pipe with mesh wick structure having opening

ABSTRACT

A plate type heat pipe includes a sealed tube, a chamber defined in the tube, and working medium received in the chamber. A mesh wick structure is attached to an inner wall of the tube. In one version of the plate type heat pipe, the wick structure defines a single opening. The opening communicates the chamber and thereby provides additional space for flow of vaporized working medium inside the tube. In other versions of the plate type heat pipe, the wick structure defines two or more openings.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to TW Patent Application No. 100148725filed on Dec. 26, 2011, the contents of which are incorporated byreference herein.

FIELD

The disclosure generally relates to heat transfer apparatuses typicallyused in electronic devices, and particularly to a plate type heat pipewith high heat transfer performance.

BACKGROUND

Heat pipes have excellent heat transfer performance and are thereforeeffective means for transfer or dissipation of heat from heat sources.Currently, heat pipes are widely used for removing heat fromheat-generating components such as central processing units (CPUs) ofcomputers. A heat pipe is usually a vacuum casing containing therein aworking medium, which is employed to carry, under phase transitionsbetween liquid state and vapor state, thermal energy from one section ofthe heat pipe (typically referring to as the “evaporator section”) toanother section thereof (typically referring to as the “condensersection”). Preferably, a wick structure is provided inside the heatpipe, lining an inner wall of the casing, for drawing the working mediumback to the evaporator section after it is condensed at the condensersection. A screen mesh inserted into the casing and held against theinner wall thereof is usually used as the wick structure of the heatpipe.

In operation, the evaporator section of the heat pipe is maintained inthermal contact with a heat-generating component. The working mediumcontained in the evaporator section absorbs heat generated by theheat-generating component and then turns into vapor. Due to thedifference in vapor pressure between the two sections of the heat pipe,the generated vapor moves and thus carries the heat towards thecondenser section where the vapor is condensed into condensate afterreleasing the heat into the ambient environment via, for example, finsthermally contacting the condenser section. Due to the difference incapillary pressure which develops in the wick structure between the twosections, the condensate is then brought back by the wick structure tothe evaporator section where it is again available for evaporation.

Typically, the screen mesh is attached to the whole inner wall of thecasing from the evaporator section to the condenser section. As aresult, a space in the heat pipe for the vaporized working medium toflow through may be inadequate. This leads to a high flow resistance forthe working medium, and thereby retards the heat transfer capability ofthe heat pipe.

Therefore, it is desirable to provide a heat pipe with improved heattransfer capability.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations of the present technology will now be described, by wayof example only, with reference to the attached figures.

FIG. 1 is an abbreviated, longitudinal cross-sectional view of a platetype heat pipe in accordance with a first embodiment of the presentdisclosure.

FIG. 2 is a transverse cross-sectional view of an adiabatic section ofthe heat pipe of the first embodiment, corresponding to line II-II ofFIG. 1.

FIG. 3 is a transverse cross-sectional view of both an evaporatorsection and a condenser section of the heat pipe of the firstembodiment, corresponding to lines III-III of FIG. 1.

FIG. 4 is a plan view of an unfolded mesh of the heat pipe of FIG. 1,showing the mesh spread out flat from a folded (or rolled) state.

FIG. 5 is a transverse cross-sectional view of an adiabatic section of aplate type heat pipe in accordance with a second embodiment of thepresent disclosure.

FIG. 6 is a plan view of an unfolded mesh of a plate type heat pipe inaccordance with a third embodiment of the present disclosure.

FIG. 7 is a plan view of an unfolded mesh of a plate type heat pipe inaccordance with a fourth embodiment of the present disclosure.

FIG. 8 is essentially a plan view of an unfolded mesh of a plate typeheat pipe in accordance with a fifth embodiment of the presentdisclosure.

FIG. 9 is a plan view of an unfolded mesh of a plate type heat pipe inaccordance with a sixth embodiment of the present disclosure.

FIG. 10 is a plan view of an unfolded mesh of a plate type heat pipe inaccordance with a seventh embodiment of the present disclosure.

FIG. 11 is a plan view of an unfolded mesh of a plate type heat pipe inaccordance with an eighth embodiment of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

It will be appreciated that for simplicity and clarity of illustration,numerous specific details are set forth in order to provide a thoroughunderstanding of the embodiments described herein. However, it will beunderstood by those of ordinary skill in the art that the embodimentsdescribed herein can be practiced without these specific details. Inother instances, methods, procedures and components have not beendescribed in detail so as not to obscure the related relevant featurebeing described. Also, the description is not to be considered aslimiting the scope of the embodiments described herein. The drawings arenot necessarily to scale and the proportions of certain parts have beenexaggerated to better illustrate details and features of the presentdisclosure. The description is not to be considered as limiting thescope of the embodiments described herein.

Several definitions that apply throughout this disclosure will now bepresented. The term “comprising” means “including, but not necessarilylimited to”; it specifically indicates open-ended inclusion ormembership in a so-described combination, group, series and the like.The term “coupled” is defined as connected, whether directly orindirectly through intervening components, and is not necessarilylimited to physical connections. The connection can be such that theobjects are permanently connected or releasably connected.

Referring to FIG. 1, a plate type heat pipe 100 in accordance with afirst embodiment of the disclosure is shown. The heat pipe 100 includesan elongated flat tube 10, which contains a wick structure 30 and aworking medium 20 therein.

Also referring to FIGS. 2-3, the tube 10 is made of a highly thermallyconductive material such as copper or aluminum. The tube 10 includes anevaporator section 102, a condenser section 104 opposite to theevaporator section 102, and an adiabatic section 103 disposed betweenthe evaporator section 102 and the condenser section 104. A thickness ofthe tube 10 from top to bottom is less than 2 mm (millimeters). That is,a total height of the tube 10 is less than 2 mm. The tube 10 includes aflat bottom wall 11, a top wall 13 opposite to the bottom wall 11, andtwo side walls 15 connected between the bottom wall 11 and the top wall13. The bottom wall 11, the top wall 13 and the side walls 15cooperatively define a sealed chamber 50. The chamber 50 is in vacuumexcept for the working medium 20.

The working medium 20 is saturated in the wick structure 30 and isusually selected from a liquid such as water, methanol, or alcohol,which has a low boiling point and is compatible with the wick structure30. Thus, the working medium 20 can easily evaporate to vapor when itabsorbs heat at the evaporator section 102 of the heat pipe 100.

The wick structure 30 is attached to an inner wall of the tube 10. Thewick structure 30 extends along an axial direction of the tube 10 fromthe evaporator section 102 to the condenser section 104. The wickstructure 30 is a porous screen mesh structure, and provides a capillaryforce to drive condensed working medium 20 at the condenser section 104to flow towards the evaporator section 102 of the heat pipe 100.

Referring also to FIG. 4, the wick structure 30 is formed by rolling arectangular mesh 31. The mesh 31 defines two rectangular openings 32spaced from each other. Each opening 32 is also spaced from an adjacentouter long edge of the mesh 31. The openings 32 are only located at theadiabatic section 103 of the heat pipe 100. In the illustratedembodiment, the openings 32 are identical, and are parallel to eachother. A transverse width of each opening 32 (measured from top tobottom in FIG. 4) is approximately one fourth of a corresponding widthof the mesh 31. A length of each opening 32 (measured from left to rightin FIG. 4) is approximately equal to a length of the adiabatic section103.

Referring to FIG. 2, a transverse cross-sectional view of the adiabaticsection 103 of the heat pipe 100 is shown. The two openings 32respectively correspond to the side walls 15 at the adiabatic section103.

Referring to FIG. 3, a transverse cross-sectional view of the evaporatorsection 102 and the condenser section 104 of the heat pipe 100 is shown.No openings are defined in portions of the wick structure 30 which arerespectively attached to the inner walls of the evaporator section 102and the condenser section 104.

FIG. 5 is a transverse cross-sectional view of the adiabatic section 103of the plate type heat pipe 100 in accordance with a second embodimentof the present disclosure. The difference between the first embodimentand the second embodiment is that in the second embodiment, the twoopenings 32 respectively corresponding to the top wall 13 and the bottomwall 11 of the tube 10 after the wick structure 30 is attached to theinner wall of the tube 10. In the illustrated embodiment, the opening 32at the top wall 13 overlaps the opening 32 at the bottom wall 11.

FIG. 6 shows an unfolded mesh 31 a for the plate type heat pipe 100 inaccordance with a third embodiment of the present disclosure. Thedifferences between the meshes 31, 31 a of the first and thirdembodiments are as follows. In the third embodiment, only one opening 32a is defined in the mesh 31 a. The opening 32 a corresponds to theadiabatic section 103 of the plate type heat pipe 100. A transversewidth of the opening 32 a is substantially half of a corresponding widthof the mesh 31 a.

FIG. 7 shows an unfolded mesh 31 b for the plate type heat pipe 100 inaccordance with a fourth embodiment of the present disclosure. Thedifferences between the meshes 31, 31 b of the first and fourthembodiments are as follows. In the fourth embodiment, the mesh 31 bdefines three spaced, parallel, rectangular openings 32 b correspondingto the adiabatic section 103 of the heat pipe 100. One of the threeopenings 32 b is defined in a middle of the mesh 31 b. The other twoopenings 32 b are respectively defined in two opposite long sides of themesh 31 b. Outer extremities of the other two openings 32 b are alignedwith opposite outer long edges of the mesh 31 b, respectively. That is,the other two openings 32 b communicate with lateral exteriors of themesh 31 b. A total transverse width of the three openings 32 b issubstantially half of a corresponding width of the mesh 31 b.

FIG. 8 shows an unfolded mesh 31 c for the plate type heat pipe 100 inaccordance with a fifth embodiment of the present disclosure. The mesh31 c defines three spaced, parallel, rectangular openings 32 ccorresponding to the adiabatic section 103 of the heat pipe 100. One ofthe three openings 32 c is defined in a middle of the mesh 31 c, and theother two openings 32 c are respectively defined in two opposite longsides of the mesh 31 c. Outer extremities of the other two openings 32 care aligned with opposite outer long edges of the mesh 31 c,respectively. That is, the other two openings 32 c communicate withlateral exteriors of the mesh 31 c. A total transverse width of thethree openings 32 c is substantially half of a corresponding width ofthe mesh 31 c. The difference between the meshes 31 b, 31 c of thefourth and fifth embodiments is, in the fifth embodiment, a copper sheet33 is connected between two opposite long side edges of the middleopening 32 c, to reinforce the strength of the mesh 31 c.

FIG. 9 shows an unfolded mesh 31 d for the plate type heat pipe 100 inaccordance with a sixth embodiment of the present disclosure. Thedifferences between the meshes 31, 31 d of the first and sixthembodiments are as follows. In the sixth embodiment, the mesh 31 ddefines six spaced rectangular openings 32 d extending in two rows alongthe axial direction of the tube 10 from the evaporator section 102 tothe condenser section 104. The two rows of openings 32 d are parallel toeach other. All the openings 32 d have a same transverse width. The twoopenings 32 d in a middle of the mesh 31 d have the same length, aredirectly opposite each other, and correspond to the adiabatic section103 of the heat pipe 100. The two openings 32 d in one of opposite endsof the mesh 31 d have the same length, are directly opposite each other,and are adjacent to the condenser section 104 of the heat pipe 100. Thetwo openings 32 d in the other opposite end of the mesh 31 d have thesame length, are directly opposite each other, and are adjacent to theevaporator section 102 of the heat pipe 100.

FIG. 10 shows an unfolded mesh 31 e for the plate type heat pipe 100 inaccordance with a seventh embodiment of the present disclosure. The mesh31 e defines an isosceles trapezoidal opening 32 e. The parallel sidesof the opening 32 e are substantially perpendicular to opposite longsides of the mesh 31 e. The opening 32 e extends along the axialdirection of the tube 10 from the evaporator section 102 to thecondenser section 104. In one embodiment, the long parallel side of theopening 32 e is adjacent to the evaporator section 102, and the shortparallel side of the opening 32 e is adjacent to the condenser section104.

FIG. 11 shows an unfolded mesh 31 f for the plate type heat pipe 100 inaccordance with an eighth embodiment of the present disclosure. The mesh31 f defines two elongated, isosceles triangular openings 32 f. In theillustrated embodiment, the openings 32 f are identical, and arearranged side by side. Bases of the openings 32 f (i.e. the twonon-equal sides of the openings 32 f) are aligned with each other, andare substantially perpendicular to opposite long sides of the mesh 31 f.Vertexes of the openings 32 f point in the same direction. The openings32 f extend along the axial direction of the tube 10 from the evaporatorsection 102 to the condenser section 104. In one embodiment, the basesof the openings 32 f are adjacent to the evaporator section 102, and thevertexes of the openings 32 f are adjacent to the condenser section 104.

According to the disclosure, a total area of the wick structure 30 isreduced due to the openings being defined in the wick structure 30,thereby increasing a space in the heat pipe 100 for the vaporizedworking medium 20 to flow therethrough. Therefore, compared withconventional heat pipes, the heat pipe 100 has not only a low flowresistance, but also a large capillary force. These advantagesfacilitate improving the heat transfer capability of the heat pipe 100.

Table 1 below shows an average of maximum heat transfer rates (Qmax) andan average of heat resistances (Rth) of a conventional mesh type heatpipe and certain of the heat pipes 100 in accordance with the presentdisclosure. The conventional mesh type heat pipe and the heat pipes 100in Table 1 all have a thickness of 1 mm. Qmax represents the maximumheat transfer rate of each heat pipe at an operational temperature of50° C. Rth is obtained by dividing the difference between an averagetemperature of the evaporator section of the heat pipe and an averagetemperature of the condenser section of the heat pipe by Qmax.

The average of Rth of the heat pipes 100 with the mesh 31 a defining oneopening 32 a is substantially equal to that of the conventional meshtype heat pipe, and the average of Qmax of the heat pipe 100 with themesh 31 a defining one opening 32 a is significantly more than that ofthe conventional mesh type heat pipe. The average of Rth of the heatpipe 100 with the mesh 31 defining two openings 32 (i.e., the heat pipeof the first embodiment) is significantly less than that of theconventional mesh type heat pipe, and the average of Qmax of the heatpipe 100 with the mesh 31 defining two openings 32 is slightly more thanthat of the conventional mesh type heat pipe. The average of Rth of theheat pipe 100 with the mesh 31 c defining three openings 32 c and thecopper sheet 33 is significantly more than that of the conventional meshtype heat pipe, and the average of Qmax of the heat pipe 100 with themesh 31 c defining three openings 32 c and the copper sheet 33 issignificantly more than that of the conventional mesh type heat pipe.

TABLE 1 Average of Qmax Average of Rth Type of heat pipe (unit: W)(unit: ° C./W) Conventional mesh type 8.1 0.6 heat pipe Heat pipe 100with the 12.5 0.61 mesh 31a defining one opening 32a Heat pipe 100 withthe 8.3 0.33 mesh 31 defining two openings 32 Heat pipe 100 with the11.9 1.07 mesh 31c defining three openings 32c and the copper sheet 33

The embodiments shown and described above are only examples. Manydetails are often found in the art such as the other features of a platetype heat pipe. Therefore, many such details are neither shown nordescribed. Even though numerous characteristics and advantages of thepresent technology have been set forth in the foregoing description,together with details of the structure and function of the presentdisclosure, the disclosure is illustrative only, and changes can be madein the detail, including in matters of shape, size and arrangement ofthe parts within the principles of the present disclosure up to, andincluding the full extent established by the broad general meaning ofthe terms used in the claims. It will therefore be appreciated that theembodiments described above can be modified within the scope of theclaims.

What is claimed is:
 1. A plate type heat pipe comprising: a sealed tubedefining a chamber therein; a working medium received in the chamber;and a mesh wick structure attached to an inner wall of the tube in thechamber, the wick structure defining at least one opening, the at leastone opening communicating with the chamber and thereby providingadditional space for flow of vaporized working medium inside the tube.2. The plate type heat pipe of claim 1, wherein the tube comprises anevaporator section, a condenser section opposite to the evaporatorsection, and an adiabatic section disposed between the evaporatorsection and the condenser section, the at least one opening beinglocated at the adiabatic section of the tube only.
 3. The plate typeheat pipe of claim 2, wherein the wick structure is a rolled meshattached on the inner wall of the tube.
 4. The plate type heat pipe ofclaim 3, wherein the at least one opening is two parallel, elongatedopenings, each of the two openings being spaced from an outer long edgeof the mesh when the mesh is unrolled and flat.
 5. The plate type heatpipe of claim 4, wherein the tube comprises a flat bottom wall, a flattop wall opposite to the bottom wall, and two side walls connectedbetween the bottom wall and the top wall, the two openings respectivelycorresponding to the top wall and the bottom wall of the tube at theadiabatic section.
 6. The plate type heat pipe of claim 4, wherein awidth of each of the openings is approximately one fourth of a width ofthe mesh when the mesh is unrolled and flat.
 7. The plate type heat pipeof claim 3, wherein the at least one opening is defined in a middle ofthe mesh.